JP2014127239A - Electrode composition, electrode and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode composition capable of materializing excellent cycle characteristic, an electrode using the same and a battery.SOLUTION: The electrode composition includes an electrode active material of which the volume is expanded/contracted in charging/discharging, and a conductive material of which the volume is expanded/contracted reversibly. The conductive material includes a hollow conductive material. The electrode composition further includes a binder for binding the electrode active material and the hollow conductive material with each other. The hollow conductive material contains a hollow conductive carbon material. The electrode active material contains at least one kind of element selected from a group comprising silicon, tin and aluminum. The electrode has a collector and an electrode composition layer formed on the collector and including the electrode composition. The battery includes at least one of the electrode.

Description

  The present invention relates to an electrode composition, an electrode using the same, and a battery. More specifically, the battery of the present invention is used as a driving power source or an auxiliary power source for motors of vehicles such as electric vehicles, fuel cell vehicles, and hybrid electric vehicles.

  In recent years, in order to cope with air pollution and global warming, reduction of carbon dioxide emissions has been strongly desired. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV). And development of the battery for motor drive which becomes the key of these practical use is performed actively.

  As a battery for driving a motor, a lithium ion battery having a high theoretical energy is attracting attention, and is currently being developed rapidly. In general, a lithium ion battery has a configuration in which a positive electrode, a negative electrode, and an electrolyte positioned therebetween are housed in a battery case. The positive electrode is formed by applying a positive electrode slurry containing a positive electrode active material to the surface of the current collector, and the negative electrode is formed by applying a negative electrode slurry containing a negative electrode active material to the surface of the current collector.

  Conventionally, an electrode sheet with improved flexibility and adhesion to the current collector can be obtained, and the electrode material can be applied thickly and the active material filling amount can be increased, resulting in high capacity and cycle characteristics. Has been proposed (see Patent Document 1).

  This battery uses a battery electrode using a binder containing a resin having a flexural modulus of 1000 MPa or less and / or a compressive modulus of elasticity of 500 MPa or less and / or a tensile modulus of elasticity of 500 MPa or less.

JP-A-9-97611

  However, since the battery described in Patent Document 1 follows the expansion and contraction of the electrode material using a binder having a low tensile elastic modulus, the electrode structure that expands and contracts can be sufficiently retained. However, there is a problem that the cycle characteristics are not sufficiently prevented from being deteriorated.

  The present invention has been made in view of such problems of the prior art. And the place made into the objective of this invention is providing the composition for electrodes which can implement | achieve the outstanding cycling characteristics, the electrode using this, and a battery.

  The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, in the electrode composition, it is found that the above-mentioned object can be achieved by including an electrode active material that expands and contracts during charge and discharge, and a conductive material that reversibly expands and contracts. The present invention has been completed.

  That is, the electrode composition of the present invention includes an electrode active material that expands and contracts during charge and discharge and a conductive material that reversibly expands and contracts.

  The electrode of the present invention is an electrode formed using the above-described electrode composition of the present invention, the electrode comprising the current collector and the electrode composition formed on the current collector And a composition layer.

  Furthermore, the battery of the present invention comprises at least one electrode of the present invention.

  According to the present invention, the electrode composition includes an electrode active material that expands and contracts during charge and discharge, and a conductive material that reversibly expands and contracts. Therefore, the composition for electrodes which can implement | achieve the outstanding cycling characteristics, the electrode using this, and a battery can be provided.

FIG. 1 is a perspective view schematically showing an external appearance of a lithium ion battery which is an embodiment of the battery according to the present invention. 2 is a schematic cross-sectional view taken along line II-II of the lithium ion battery shown in FIG. FIG. 3 is a perspective view schematically showing a configuration of an electrode for a lithium ion battery which is an embodiment of the electrode according to the present invention. FIG. 4 is a diagram for explaining the outline in a charged state (a) and a discharged state (b) of a negative electrode for a lithium ion battery which is an embodiment of the electrode according to the present invention. FIG. 5 is a perspective view schematically showing a configuration of an electrode for a lithium ion battery which is one form of a conventional electrode. FIG. 6 is a diagram for explaining the outline of the state of charge (a) and the state of discharge (b) of a negative electrode for a lithium ion battery, which is an embodiment of a conventional electrode. FIG. 7 is a graph showing the cycle characteristics of each example.

  Hereinafter, the composition for an electrode according to the present invention, and the form of an electrode and a battery using the composition will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  Hereinafter, basic configurations of an electrode and a battery to which the electrode composition of the present invention can be applied will be described with reference to the drawings. In this embodiment, a lithium ion battery will be described as an example.

  First, the lithium ion battery in this embodiment has a large cell (single cell layer) voltage, and can achieve high energy density and high output density. Therefore, the lithium ion battery of this embodiment is excellent for use as a vehicle drive power supply or auxiliary power supply. As a result, it can be suitably used as a lithium ion battery for a vehicle drive power source or the like. In addition to this, the present invention can be sufficiently applied to lithium ion batteries for portable devices such as mobile phones.

  Moreover, the lithium ion battery in this form should just use the electrode composition for lithium ion batteries of this form demonstrated below, and it does not restrict | limit in particular regarding another component requirement.

  For example, the usage form of the lithium ion battery may be used for either a lithium ion primary battery or a lithium ion secondary battery. In particular, since it is excellent in cycle characteristics, it is preferable to use it as a lithium ion secondary battery for a vehicle driving power source or a portable device such as a cellular phone.

  Further, when the lithium ion battery is distinguished by its form and structure, it can be applied to any conventionally known form and structure such as a stacked (flat) battery or a wound (cylindrical) battery. . For example, by adopting a laminated (flat) battery structure, it is possible to secure long-term reliability by applying sealing technology such as simple thermocompression using a laminated film, which is advantageous in terms of cost and workability. It is. Of course, the present invention is not limited to such a laminate type battery, and can be applied to any conventionally known form / structure such as a button type battery, a coin type battery, a rectangular or cylindrical can type battery.

  Furthermore, when viewed in terms of electrical connection form (electrode structure) in a lithium ion battery, it can be applied to both non-bipolar (internal parallel connection type) batteries and bipolar (internal series connection type) batteries. is there. A battery element in a bipolar battery generally has a bipolar electrode in which a negative electrode active material layer is formed on one surface of a current collector and a positive electrode active material layer is formed on the other surface, and an electrolyte layer. A plurality of layers.

  Furthermore, when distinguished by the type of electrolyte layer in the lithium ion battery, a solution electrolyte type battery using a solution electrolyte such as a non-aqueous electrolyte solution for the electrolyte layer, a polymer battery using a polymer electrolyte for the electrolyte layer It can be applied to any conventionally known electrolyte layer type. The polymer battery further includes a gel electrolyte type battery using a polymer gel electrolyte (also simply referred to as a gel electrolyte) and a solid polymer (all solid) type battery using a polymer solid electrolyte (also simply referred to as a polymer electrolyte). It is divided into.

  Therefore, in the following description, a non-bipolar (internal parallel connection type) lithium ion battery using an electrode composition for a lithium ion battery will be described in detail with reference to the drawings.

[battery]
FIG. 1 is a perspective view schematically showing an external appearance of a lithium ion battery which is an embodiment of the battery according to the present invention. 2 is a schematic cross-sectional view taken along line II-II of the lithium ion battery shown in FIG. Such a lithium ion battery is called a laminate type lithium ion battery.

  As shown in FIGS. 1 and 2, the lithium ion battery 1 has a configuration in which a battery element 10 to which a positive electrode lead 21 and a negative electrode lead 22 are attached is enclosed in an exterior body 30 formed of a laminate film. ing. In this embodiment, the positive electrode lead 21 and the negative electrode lead 22 are led out in the opposite direction from the inside of the exterior body 30 to the outside. Although not shown, the positive electrode lead and the negative electrode lead may be led out in the same direction from the inside of the exterior body toward the outside. Moreover, such a positive electrode lead and a negative electrode lead can be attached to a positive electrode current collector and a negative electrode current collector, which will be described later, by ultrasonic welding or resistance welding, for example.

  The positive electrode lead 21 and the negative electrode lead 22 are made of, for example, a metal material such as aluminum (Al), copper (Cu), titanium (Ti), nickel (Ni), alloys thereof, and stainless steel (SUS). However, the material is not limited thereto, and a conventionally known material used as a lead for a lithium ion battery can be used.

  The positive electrode lead and the negative electrode lead may be made of the same material or different materials. Further, as in this embodiment, a separately prepared lead may be connected to a positive electrode current collector and a negative electrode current collector described later, and each positive electrode current collector and each negative electrode current collector described later are extended. The lead may be formed by Although not shown, the positive lead and the negative lead taken out from the exterior body do not affect products (for example, automobile parts, especially electronic devices) by contacting with peripheral devices or wiring and causing electric leakage. Thus, it is preferable to coat with a heat-resistant insulating heat-shrinkable tube or the like.

  Further, although not shown, a current collector plate may be used for the purpose of taking out the current outside the battery. The current collector plate is electrically connected to a current collector or a lead, and is taken out of a laminate film that is an exterior material of the battery. The material which comprises a current collector plate is not specifically limited, The well-known highly electroconductive material conventionally used as a current collector plate for lithium ion batteries can be used. As a constituent material of the current collector plate, for example, metal materials such as aluminum (Al), copper (Cu), titanium (Ti), nickel (Ni), alloys thereof, and stainless steel (SUS) are preferable, and light weight and corrosion resistance. From the viewpoint of high conductivity, aluminum (Al), copper (Cu), and the like are more preferable. Note that the same material may be used for the positive electrode current collector plate and the negative electrode current collector plate, or different materials may be used.

  For example, the exterior body 30 is preferably formed of a film-shaped exterior material from the viewpoint of miniaturization and weight reduction, but is not limited to this, and the exterior body for a lithium ion battery is not limited thereto. Any conventionally known one can be used. That is, a metal can case can also be applied.

  In addition, from the viewpoint that it is excellent in high output and cooling performance, and can be suitably used for batteries for large equipment such as electric vehicles and hybrid electric vehicles, for example, a polymer-metal composite laminate film excellent in thermal conductivity. Is preferably applied. More specifically, an outer package formed of a three-layer laminated film outer package in which polypropylene as a thermocompression bonding layer, aluminum as a metal layer, and nylon as an outer protective layer are laminated in this order is suitably used. Can be used.

  Note that the exterior body may be constituted by another structure, for example, a laminate film not having a metal material, a polymer film such as polypropylene, or a metal film, instead of the above-described laminate film.

  Here, the general structure of an exterior body can be represented by the laminated structure of an external protective layer / metal layer / thermocompression bonding layer (however, the external protective layer and the thermocompression bonding layer may be composed of a plurality of layers. .) As the metal layer, it is sufficient to function as a moisture-permeable barrier film, and not only aluminum foil, but also stainless steel foil, nickel foil, plated iron foil, etc. can be used, but it is thin and lightweight. Thus, an aluminum foil excellent in workability can be suitably used.

  The structures that can be used as the exterior body are listed in the form of (external protective layer / metal layer / thermocompression layer). Terephthalate / unstretched polypropylene, polyethylene terephthalate / nylon / aluminum / unstretched polypropylene, polyethylene terephthalate / nylon / aluminum / nylon / unstretched polypropylene, polyethylene terephthalate / nylon / aluminum / nylon / polyethylene, nylon / polyethylene / aluminum / linear Low density polyethylene, polyethylene terephthalate / polyethylene / aluminum / polyethylene terephthalate / Density polyethylene, and a polyethylene terephthalate / nylon / aluminum / low density polyethylene / cast polypropylene.

  As shown in FIG. 2, the battery element 10 includes a positive electrode 11 in which a positive electrode active material layer 11B is formed on both main surfaces of the positive electrode current collector 11A, an electrolyte layer 13, and a negative electrode current collector 12A. A plurality of negative electrodes 12 each having a negative electrode active material layer 12B formed on both main surfaces are stacked. At this time, the electrode composition described later in detail is included in either or both of the positive electrode active material layer 11B and the negative electrode active material layer 12B. Further, the positive electrode active material layer 11B formed on one main surface of the positive electrode current collector 11A of one positive electrode 11 and the one main surface of the negative electrode current collector 12A of the negative electrode 12 adjacent to the one positive electrode 11 The negative electrode active material layer 12 </ b> B formed on the surface of the substrate faces the electrolyte layer 13. In this way, a plurality of positive electrodes 11, electrolyte layers 13, and negative electrodes 12 are stacked in this order.

  As a result, the adjacent positive electrode active material layer 11B, electrolyte layer 13 and negative electrode active material layer 12B constitute one unit cell layer. Therefore, in this embodiment, the lithium ion battery 1 has a configuration in which a plurality of single battery layers 14 are stacked and electrically connected in parallel. In addition, the positive electrode and the negative electrode may have each active material layer formed on one main surface of each current collector. In this embodiment, for example, the negative electrode current collector 12a located in the outermost layer of the battery element 10 has the negative electrode active material layer 12B formed only on one side.

  In addition, an insulating layer (not shown) may be provided on the outer periphery of the unit cell layer to insulate between the adjacent positive electrode current collector and negative electrode current collector. Such an insulating layer is preferably formed of, for example, a material that holds the electrolyte contained in the electrolyte layer and the like and prevents electrolyte leakage from the outer periphery of the single cell layer. Specifically, polypropylene (PP), polyethylene (PE), polyurethane (PUR), polyamide resin (PA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polystyrene (PS), polyimide (PI) ) General-purpose plastics such as SBR and thermoplastic olefin rubbers can be used. Silicone rubber can also be used.

[Electrode and electrode composition]
FIG. 3 is a perspective view schematically showing a configuration of an electrode for a lithium ion battery which is an embodiment of the electrode according to the present invention. As shown in FIG. 3, an electrode 50 for a lithium ion battery includes a current collector 51A and an electrode composition layer 51B formed on the current collector 51A. The electrode composition layer 51B includes an electrode composition 60. The electrode composition 60 includes an electrode active material 61 that expands and contracts during charge and discharge, a conductive material 62 that reversibly expands and contracts, and an electrode. It includes a binding material 63 that binds the active material 61 and the conductive material 62 to each other. In addition, the electrode 50 for lithium ion batteries is applicable to any one or both of a positive electrode and a negative electrode. At this time, constituent members and materials such as the current collector 51A, the electrode active material 61, the conductive material 62, and the binder 63 can be appropriately selected according to the polarity of the applied electrode. In addition, the electrode for a lithium ion battery is applied to a negative electrode for a lithium ion battery to which a negative electrode active material that expands and contracts by volume during charge / discharge is applied, depending on the type of positive electrode active material and negative electrode active material to be applied. Is preferred. If the contact between the electrode active material and the conductive material can be maintained, the binder is not an essential constituent material but can be added as necessary.

[Mechanism in electrode]
Moreover, FIG. 4 is a figure explaining the outline in the charge state (a) and discharge state (b) of the negative electrode for lithium ion batteries which is one form of the electrode which concerns on this invention. As shown in FIG. 4, an electrode 50 for a lithium ion battery includes a current collector 51A and an electrode composition layer 51B formed on the current collector 51A. The negative electrode composition layer, which is an example of the electrode composition layer 51B, includes a negative electrode active material 61a, a conductive material 62a, and a binder 63a that binds the negative electrode active material 61a and the conductive material 62a to each other. Composition 60a is included. In the charged state, the negative electrode active material 61a that occludes lithium expands, and the conductive material 62a contracts by receiving a force directly or through the binder 63a, thereby avoiding the destruction of the electrode composition layer 51B. Is done. As a result, the cycle characteristics of the battery are improved. Further, in the discharge state, as the negative electrode active material 61a that has released lithium contracts, the conductive material 62a expands due to the restoring force, thereby avoiding the generation of voids and avoiding the cutting of the conductive path. . As a result, the cycle characteristics of the battery are improved. In addition, since the destruction of the electrode composition layer due to the volume expansion and contraction of the electrode active material during charging and discharging can be avoided by adding a predetermined conductive material, for example, in the case of a silicon-based negative electrode, at present, the electrode destruction In order to avoid this, about 20% of the theoretical capacity is used, but the usage rate can be increased, and further higher energy density and higher output can be achieved.

  Although not shown, when applied to a positive electrode for a lithium ion battery, the positive electrode active material from which lithium is released contracts in a charged state, and a conductive material expands due to restoring force, thereby generating voids. Is avoided and disconnection of the conductive path is avoided. In addition, in the discharge state, as the positive electrode active material that occludes lithium expands, the conductive material contracts by receiving a force directly or through a binder, thereby destroying the electrode composition layer. Is avoided. As a result, the cycle characteristics of the battery are improved.

  On the other hand, FIG. 5 is a perspective view schematically showing a configuration of an electrode for a lithium ion battery which is one form of a conventional electrode. As shown in FIG. 5, an electrode 70 for a lithium ion battery includes a current collector 71A and an electrode composition layer 71B formed on the current collector 71A. The electrode composition layer 71B includes an electrode composition 80. The electrode composition 80 includes an electrode active material 81 that expands and contracts during charge and discharge, a conductive material 82 that does not reversibly expand and contract, and an electrode. A binder 83 that binds the active material 81 and the conductive material 82 to each other.

  Moreover, FIG. 6 is a figure explaining the outline in the charge state (a) and discharge state (b) of the negative electrode for lithium ion batteries which is one form of the conventional electrode. As shown in FIG. 6, an electrode 70 for a lithium ion battery includes a current collector 71A and an electrode composition layer 71B formed on the current collector 71A. The negative electrode composition layer, which is an example of the electrode composition layer 71B, includes a negative electrode active material 81a, a conductive material 82a, and a binder 83a that binds the negative electrode active material 81a and the conductive material 82a to each other. Contains composition 80a. In the charged state, the negative electrode active material 81a that occludes lithium expands. As a result, the conductive material 82a does not contract even if it receives a force directly or through the binder 83a, so that the electrode composition layer 71B is destroyed. proceed. As a result, the cycle characteristics of the battery are degraded. Further, in the discharged state, the conductive material 82a does not expand as the negative electrode active material 81a that has released lithium contracts, whereby a void is generated and the conductive path is cut. As a result, the cycle characteristics of the battery are degraded.

  Hereinafter, each configuration will be described in detail.

(Current collector)
The positive electrode current collector 11A and the negative electrode current collector 12A are made of a conductive material. The size of the current collector can be determined according to the intended use of the battery. For example, if it is used for a large battery that requires a high energy density, a current collector having a large area is used. The thickness of the current collector is not particularly limited. The thickness of the current collector is usually about 1 to 100 μm. Further, the shape of the current collector is not particularly limited. In the battery element 10 shown in FIG. 2, in addition to the current collector foil, a mesh-shaped one (expanded grid or the like) can be used. In addition, when forming the thin film alloy which is an example of a negative electrode active material directly on the negative electrode collector 12A by sputtering method etc., it is preferable to use current collection foil.

  There are no particular limitations on the material constituting the current collector. For example, a metal or a resin in which a conductive filler is added to a conductive polymer material or a non-conductive polymer material can be employed.

  The amount of the conductive filler added is not particularly limited as long as it is an amount capable of imparting sufficient conductivity to the current collector, and is generally about 5 to 35% by mass. However, the material is not limited thereto, and a conventionally known material used as a current collector for a lithium ion battery can be used.

(Electrode active material)
The electrode active material included as an essential constituent material is not particularly limited as long as it expands and contracts during charge and discharge, and a positive electrode active material and a negative electrode active material applied to conventional lithium ion batteries are applied. can do. In the present invention, “the one that expands and contracts during charging / discharging” is not limited to the one that expands during charging and contracts during discharging, but contracts during charging and expands during discharging. Must be interpreted to include. The shape and constituent elements of the electrode active material can be specified by observation with a scanning electron microscope (SEM) or analysis by energy dispersive X-ray fluorescence spectroscopy (EDX).

  As a typical positive electrode active material in a lithium ion battery, a positive electrode material capable of inserting and extracting lithium can be given. As such a positive electrode material, for example, a lithium-containing compound is preferable from the viewpoint of capacity and output characteristics. Examples of such lithium-containing compounds include composite oxides containing lithium and transition metal elements, phosphate compounds containing lithium and transition metal elements, sulfate compounds containing lithium and transition metal elements, and lithium and transition metals. A solid solution containing an element can be mentioned, and a lithium-transition metal composite oxide is particularly preferable from the viewpoint of obtaining higher capacity and output characteristics.

Specific examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (LiCoO ₂ ), lithium nickel composite oxide (LiNiO ₂ ), lithium nickel cobalt composite oxide (LiNiCoO ₂ ), and lithium nickel. Manganese composite oxide (LiNi _0.5 Mn _1.5 O ₄ ), lithium nickel manganese cobalt composite oxide (Li (NiMnCo) O ₂ , Li (LiNiMnCo) O ₂ ), lithium manganese composite oxide having a spinel structure (LiMn ₂ O ₄ ) and the like. Specific examples of the phosphate compound containing lithium and a transition metal element include a lithium iron phosphate compound (LiFePO ₄ ) and a lithium iron manganese phosphate compound (LiFeMnPO ₄ ). In these composite oxides, for example, for the purpose of stabilizing the structure, a part of the transition metal may be substituted with another element.

As a specific example of a solid solution containing lithium and a transition metal element, xLiM ^I O _2. (1-x) Li ₂ M ^II O ₃ (0 <x <1, M ^I is an average oxidation state 3+, M ^II is an average And one or more transition metal elements having an oxidation state of 4+), LiM ^III O ₂ —LiMn ₂ O ₄ (M ^III is a transition metal element such as Ni, Mn, Co, or Fe). In addition, you may use positive electrode active materials other than the above, for example, a lithium metal can also be used. These positive electrode active materials may be used alone or in combination of two or more. However, it is not limited to these, The conventionally well-known material used as a positive electrode active material for lithium ion batteries can be used.

As a typical negative electrode active material in a lithium ion battery, there can be mentioned lithium, a lithium alloy, or a negative electrode material capable of inserting and extracting lithium. Examples of such negative electrode materials include silicon (Si), germanium (Ge), tin (Sn), lead (Pb), aluminum (Al), indium (In), zinc (Zn), hydrogen (H), Calcium (Ca), strontium (Sr), barium (Ba), ruthenium (Ru), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), Cadmium (Cd), mercury (Hg), gallium (Ga), thallium (Tl), carbon (C), nitrogen (N), antimony (Sb), bismuth (Bi), oxygen (O), sulfur (S), Elemental elements and alloys of elements to be alloyed with lithium such as selenium (Se), tellurium (Te) and chlorine (Cl), and oxides containing these elements (silicon monoxide (SiO), SiO _x (0 <x < 2), Tin oxide _{(SnO 2), SnO x (} 0 <x <2), etc. SnSiO ₃₎ and carbides such as (silicon carbide (SiC)) or the like; a metal material of a lithium metal or the like; lithium - titanium composite oxide (lithium titanate : Lithium-transition metal composite oxides such as: Li ₄ Ti ₅ O ₁₂ ).

Among them, those containing elements such as silicon (Si), tin (Sn), and aluminum (Al) are suitable as the negative electrode active material. These can be applied alone or in combination of two or more. Moreover, as a suitable example of the (Si type) negative electrode active material containing silicon (Si), an Si-M alloy (M is made of zinc (Zn), tin (Sn), titanium (Ti), and aluminum (Al)). And at least one element selected from the group) and silicon monoxide (SiO). Here, SiO includes amorphous silicon partially made of SiO ₂ . The Si-based negative electrode active material is particularly preferable as an example to which the present invention is applied because the volume of the Si-based negative electrode active material may expand to about 4 times during charging.

  Other than the above, graphite (natural graphite, artificial graphite, etc.), low crystalline carbon (soft carbon, hard carbon), carbon black (Ketjen black, acetylene black, channel black, lamp black, oil) Furnace black, thermal black, etc.), fullerenes, carbon nanotubes, carbon nanofibers, carbon nanohorns, carbon fibrils and other negative electrode active materials may be used.

  Moreover, these negative electrode active materials may be used individually by 1 type, and may use 2 or more types together. However, it is not limited to these, The conventionally well-known material used as a negative electrode active material for lithium ion batteries can be used.

  In addition, when the optimum particle diameter is different in expressing the unique effect of each active material, the optimum particle diameters may be mixed and used for expressing each unique effect. There is no need to make the particle size of the material uniform. For example, when an oxide in the form of particles is used as the positive electrode active material, the average particle size of the oxide may be approximately the same as the average particle size of the positive electrode active material included in the existing positive electrode active material layer, and is not particularly limited. . From the viewpoint of increasing the output, it is preferably in the range of 1 to 20 μm. Further, for example, when a particle-form alloy is used as the negative electrode active material, the average particle size of the alloy may be approximately the same as the average particle size of the negative electrode active material contained in the existing negative electrode active material layer, and is not particularly limited. . From the viewpoint of increasing the output, it is preferably in the range of 1 to 20 μm. However, it is not limited to such a range, and it goes without saying that it may be outside this range as long as the effects of the present invention can be effectively expressed.

  In the present specification, the “particle diameter” is the contour line of the active material particles (observation surface) observed using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). It means the maximum distance among the distances between any two points. As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

  The particle diameters and average particle diameters of other components can be defined in the same manner. However, it is not limited to such a range, and it goes without saying that it may be outside this range as long as the effects of the present invention can be effectively expressed.

(Conductive material)
The conductive material as the essential constituent material is not particularly limited as long as it can reversibly expand and contract in volume. For example, a hollow conductive material such as a hollow conductive carbon material or a hollow conductive resin can be applied. Examples of the hollow conductive carbon material include fullerene, a carbon nanopipe cell, and a carbon balloon. The hollow conductive carbon material is preferable from the viewpoint that the electrode performance can be improved at low cost and at low cost. Specific examples of carbon balloons include lignin black. Only a material that reversibly expands and contracts, such as lignin black, may be applied as a conductive material, but a conventionally known material used as a conductive material for a lithium ion battery may be added as appropriate. Specifically, carbon materials, such as carbon black, such as acetylene black, a graphite, and a vapor growth carbon fiber, can be mentioned, for example. Moreover, you may use together the conductive binder which has the function of a conductive material and a binder together with the conductive material as an essential constituent material. As the conductive binder, for example, commercially available TAB-2 (manufactured by Hosen Co., Ltd.) can be used.

(Binder)
Although it does not specifically limit as a binder, For example, the following materials are mentioned.
Polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), polyacrylonitrile (PAN), polyimide (PI), polyamide (PA), cellulose, carboxymethylcellulose (CMC), ethylene-acetic acid Vinyl copolymer, polyvinyl chloride (PVC), styrene / butadiene rubber (SBR), isoprene rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer, and Its hydrogenated product, thermoplastic polymer such as styrene / isoprene / styrene block copolymer and its hydrogenated product, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoro Tylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / Fluoropolymers such as chlorotrifluoroethylene copolymer (ECTFE) and polyvinyl fluoride (PVF), vinylidene fluoride-hexafluoropropylene fluororubber (VDF-HFP fluoropolymer), vinylidene fluoride-hexafluoropropylene-tetra Fluoroethylene fluoro rubber (VDF-HFP-TFE fluoro rubber), vinylidene fluoride-pentafluoropropylene fluoro rubber (VDF-PFP fluoro rubber), vinylidene fluoride- Interfluoropropylene-tetrafluoroethylene fluorine rubber (VDF-PFP-TFE fluorine rubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluorine rubber (VDF-PFMVE-TFE fluorine rubber), vinylidene fluoride -Vinylidene fluoride-based fluororubber such as chlorotrifluoroethylene-based fluororubber (VDF-CTFE-based fluororubber), epoxy resin and the like. Among these, polyvinylidene fluoride, polyimide, styrene / butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable. These suitable binders are excellent in heat resistance, have a very wide potential window, are stable at both the positive electrode potential and the negative electrode potential, and can be used for the positive electrode (and negative electrode) active material layer. However, the material is not limited to these, and a known material conventionally used as a binder for a lithium ion battery can be used. These binders may be used alone or in combination of two or more.

  The amount of the binder contained in the electrode active material layer is not particularly limited as long as it is an amount capable of binding the electrode active material and the conductive material, but is preferably 0 with respect to the electrode active material layer. It is 5-15 mass%, More preferably, it is 1-10 mass%.

  Further, the thickness of each active material layer (active material layer on one side of the current collector) is not particularly limited, and conventionally known knowledge about the battery can be referred to as appropriate. For example, the thickness of each active material layer is usually about 1 to 500 μm, preferably 2 to 100 μm in consideration of the intended use of the battery (emphasis on output, energy, etc.) and ion conductivity.

(Electrolyte layer)
As the electrolyte layer 13, for example, an electrolyte solution, a polymer gel electrolyte, a solid polymer electrolyte formed in a separator described later, and a layer structure formed using a solid polymer electrolyte, or a polymer gel electrolyte or a solid polymer electrolyte are used. Examples thereof include those having a laminated structure formed thereon.

For example, it is preferable that the electrolytic solution is usually used in a lithium ion battery. Specifically, the electrolytic solution has a form in which a supporting salt (lithium salt) is dissolved in an organic solvent. Examples of the lithium salt include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), six Inorganic acid anion salts such as lithium fluorotantalate (LiTaF ₆ ), lithium tetrachloroaluminate (LiAlCl ₄ ), lithium decachlorodecaborate (Li ₂ B ₁₀ Cl ₁₀ ), lithium trifluoromethanesulfonate (LiCF ₃₎ Organic acids such as SO ₃ ), lithium bis (trifluoromethanesulfonyl) imide (Li (CF ₃ SO ₂ ) ₂ N), lithium bis (pentafluoroethanesulfonyl) imide (Li (C ₂ F ₅ SO ₂ ) ₂ N) List at least one lithium salt selected from anionic salts Can. Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC) and ethylene carbonate (EC); chain carbonates such as dimethyl carbonate (DMC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC). Ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; lactones such as γ-butyrolactone; nitriles such as acetonitrile; methyl propionate; Esters such as amides; Amides such as dimethylformamide; One using at least one selected from methyl acetate and methyl formate, or a mixture using an organic solvent such as an aprotic solvent can be used. . Examples of the separator include a microporous film made of polyolefin such as polyethylene (PE) and polypropylene (PP), a porous flat plate, and a nonwoven fabric.

  Examples of the polymer gel electrolyte include those containing a polymer constituting the polymer gel electrolyte and an electrolytic solution in a conventionally known ratio. For example, from the viewpoint of ionic conductivity and the like, it is desirable to set it to about several mass% to 98 mass%. The polymer gel electrolyte is a solid polymer electrolyte having ion conductivity containing the above-described electrolytic solution usually used in a lithium ion battery. However, the present invention is not limited to this, and includes a structure in which a similar electrolyte solution is held in a polymer skeleton having no lithium ion conductivity.

  Examples of the polymer having no lithium ion conductivity used in the polymer gel electrolyte include polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA). Can be used. However, it is not necessarily limited to these. In addition, since polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and the like are in a class that has almost no ionic conductivity, it can be a polymer having the ionic conductivity. Here, the polymer used for the polymer gel electrolyte is exemplified as a polymer having no lithium ion conductivity.

  Examples of the solid polymer electrolyte include a structure in which the lithium salt is dissolved in polyethylene oxide (PEO), polypropylene oxide (PPO), and the like, and does not contain an organic solvent. Therefore, when the electrolyte layer is composed of a solid polymer electrolyte, there is no fear of liquid leakage from the battery, and the battery reliability can be improved.

  The thickness of the electrolyte layer is preferably thinner from the viewpoint of reducing internal resistance. The thickness of the electrolyte layer is usually 1 to 100 μm, preferably 5 to 50 μm. A polymer gel electrolyte or a solid polymer electrolyte matrix polymer can exhibit excellent mechanical strength by forming a cross-linked structure. In order to form a crosslinked structure, a suitable polymerization initiator is used to polymerize a polymer for forming a polymer electrolyte (for example, polyethylene oxide (PEO) or polypropylene oxide (PPO)) by thermal polymerization, ultraviolet polymerization, A polymerization treatment such as radiation polymerization or electron beam polymerization may be performed.

Next, an example is given and demonstrated about the manufacturing method of the lithium ion battery mentioned above.
First, a positive electrode is produced. For example, when a granular positive electrode active material is used, the positive electrode active material described above is mixed with a conductive material, a binder, and a viscosity adjusting solvent that are added as necessary to prepare a positive electrode slurry. Next, this positive electrode slurry is applied to a positive electrode current collector, dried, and compression molded to form a positive electrode active material layer.

  Moreover, a negative electrode is produced. For example, when using a granular negative electrode active material, a negative electrode active material that expands and contracts during charging and discharging, and a conductive material that reversibly expands and contracts, and a binder and a viscosity adjusting solvent that are added as necessary are mixed. A negative electrode slurry is prepared. Thereafter, the negative electrode slurry is applied to a negative electrode current collector, dried, and compression molded to form a negative electrode active material layer.

  Next, the positive electrode lead is attached to the positive electrode and the negative electrode lead is attached to the negative electrode, and then the positive electrode, the separator, and the negative electrode are laminated. Further, the laminated product is sandwiched between polymer-metal composite laminate sheets, and the outer peripheral edge except one side is heat-sealed to form a bag-like exterior body.

  After that, a non-aqueous electrolyte containing a lithium salt such as lithium hexafluorophosphate and an organic solvent such as ethylene carbonate is prepared and injected into the interior through the opening of the exterior body, and the opening of the exterior body is thermally melted. Wear and enclose. Thereby, a laminate-type lithium ion battery is completed.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples.

Example 1
<Production of negative electrode>
First, SiO (average particle diameter: 5 μm) as a negative electrode active material, lignin black and carbon black as conductive materials, and polyvinylidene fluoride (PVDF) as a binder are 80: 2.5: 2.5: 15. The solid content was obtained by kneading at a mass ratio of Next, an appropriate amount of N-methyl-2-pyrrolidone (NMP), which is a slurry viscosity adjusting solvent, was added to the obtained solid content to obtain a slurry for a negative electrode composition layer. Thereafter, the obtained slurry for negative electrode composition layer is applied to one main surface of a copper foil (thickness: 10 μm) as a negative electrode current collector, dried, and then applied to the other main surface. It was dried and pressed to obtain a negative electrode having a negative electrode composition layer on both main surfaces of the negative electrode current collector.

<Preparation of positive electrode>
LiMnO ₂ (average particle size: 10 μm) as a positive electrode active material, acetylene black (average particle size: 0.1 μm) as a conductive material, and PVDF as a binder were kneaded at a mass ratio of 85: 5: 10. A solid was obtained. Next, an appropriate amount of NMP, which is a slurry viscosity adjusting solvent, was added to the obtained solid content to obtain a positive electrode composition layer slurry. Thereafter, the obtained slurry for the positive electrode composition layer is applied to one main surface of an aluminum foil (thickness: 10 μm) as a positive electrode current collector, dried, and then applied to the other main surface. It was dried and pressed to obtain a positive electrode having a positive electrode composition layer on both main surfaces of the positive electrode current collector.

<Preparation of electrolyte>
Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 2 to obtain a solvent. Thereafter, an electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) as a supporting salt in the obtained solvent so as to have a concentration of 1 mol / L.

<Production of battery>
Leads were welded to the current collector portions of the positive electrode and the negative electrode. A laminate was prepared by sandwiching a porous polypropylene separator between the negative electrode and the positive electrode welded with these leads. Subsequently, the laminate was made of aluminum laminate film, sandwiched on both sides of the laminate, and sealed by thermocompression bonding on three sides. After injecting a mixed solution as an electrolytic solution into this laminate, the remaining one side was thermocompression sealed to produce a laminate type lithium ion battery as shown in FIG.

(Example 2)
In preparation of the negative electrode, SiO (average particle diameter: 5 μm) as the negative electrode active material, lignin black and carbon black as the conductive material, and polyvinylidene fluoride (PVDF) as the binder were 80: 5: 0: 15 A solid content is obtained by kneading at a mass ratio, and then an appropriate amount of N-methyl-2-pyrrolidone (NMP), which is a slurry viscosity adjusting solvent, is added to the obtained solid content to obtain a slurry for a composition layer for a negative electrode. Then, after applying and drying the obtained slurry for negative electrode composition layer on one main surface of a copper foil (thickness: 10 μm) as a negative electrode current collector, the other main surface also The same operation as in Example 1 was repeated except that a negative electrode having a negative electrode composition layer on both main surfaces of a negative electrode current collector obtained by applying, drying and pressing was used. An example lithium ion battery was obtained.

(Comparative Example 1)
In preparation of the negative electrode, SiO (average particle diameter: 5 μm) as a negative electrode active material, acetylene black (average particle diameter: 0.1 μm) as a conductive material, and polyvinylidene fluoride (PVDF) as a binder are 80: 5. : Knead | mixed by 15 mass ratio, solid content was obtained, then, N-methyl- 2-pyrrolidone (NMP) which is a slurry viscosity adjustment solvent was added to the obtained solid content, and the composition layer for negative electrodes The slurry for an anode was obtained, and then the obtained slurry for a composition layer for a negative electrode was applied to one main surface of a copper foil (thickness: 10 μm) as a negative electrode current collector and then dried. The same operation as in Example 1 was repeated except that the negative electrode having the negative electrode composition layer was used on both main surfaces of the negative electrode current collector obtained by applying the coating onto the surface, drying, and pressing. Thus, a lithium ion battery of this example was obtained.

[Performance evaluation]
The lithium ion batteries of the above examples were charged in the air at 25 ° C. for 13 hours by the constant current and constant voltage method (CCCV, current: 0.1 C, voltage: 4.2 V). Next, after resting for 10 minutes, discharge treatment was performed to 2.5 V by a constant current method (CC, current: 0.1 C).

  Subsequently, after 10 minutes of rest, the battery was charged for 3 hours by a constant current constant voltage method (CCCV, current: 1 C, voltage 4.2 V). Thereafter, the battery was discharged to 2.5 V by a constant current method (CC, current: 0.1 C), and the discharge capacity was measured. These cycles were repeated (cycle test), and the value of the discharge capacity in each cycle was calculated. The obtained results are shown in FIG.

  FIG. 7 shows that Example 1 and Example 2 belonging to the scope of the present invention have excellent cycle characteristics as compared with Comparative Example 1 outside the present invention.

  Although the present invention has been described above with some specific examples, the present invention is not limited to these, and various modifications are possible within the scope of the gist of the present invention.

  That is, in the above specific example, the electrode for the lithium ion battery is exemplified as the electrode to which the electrode composition is applied. However, the present invention is not limited to this, and the electrode composition of the present invention is an electrode for a capacitor. It can also be applied to.

DESCRIPTION OF SYMBOLS 1 Lithium ion battery 10 Battery element 11 Positive electrode 11A Positive electrode collector 11B Positive electrode active material layer 12 Negative electrode 12A, 12a Negative electrode collector 12B Negative electrode active material layer 13 Electrolyte layer 14 Single battery layer 21 Positive electrode lead 22 Negative electrode lead 30 Exterior body 50 70 Electrode 51A, 71A Current collector 51B, 71B Electrode composition layer 60, 80 Electrode composition 60a, 80a Negative electrode composition 61, 81 Electrode active material 61a, 81a that expands and contracts during charge / discharge Charge / discharge Negative electrode active materials 62, 62a that expand and contract by volume Conductive materials 63, 63a, 83, 83a that reversibly expand and contract binders 82, 82a Conductive materials that do not reversibly expand and contract by volume

Claims (7)

An electrode active material that expands and contracts during charge and discharge; and
And a conductive material that reversibly expands and contracts in volume.   The electrode composition according to claim 1, wherein the conductive material contains a hollow conductive material. A binder that binds the electrode active material and the hollow conductive material to each other;
The electrode composition according to claim 2, wherein the hollow conductive material contains a hollow conductive carbon material.   The electrode active material according to any one of claims 1 to 3, wherein the electrode active material is an electrode active material containing at least one element selected from the group consisting of silicon, tin and aluminum. Composition. An electrode formed using the electrode composition according to any one of claims 1 to 4,
An electrode comprising: a current collector; and an electrode composition layer including the electrode composition formed on the current collector.   A battery comprising at least one electrode according to claim 5.   The battery according to claim 6, wherein the battery is a lithium ion secondary battery.

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